Anthony Waugh

Measurement of hard double-parton interactions in W(to lv) positive 2-jet events at square root of s equals to TeV with the ATLAS detector

The production of W bosons in association with two jets in proton-proton collisions at a centre-of-mass energy of root s = 7 TeV has been analysed for the presence of double-parton interactions using data corresponding to an integrated luminosity of 36 pb(-1), collected with the ATLAS detector at the Large Hadron Collider. The fraction of events arising from double-parton interactions, f(DP)((D)), has been measured through the p(T) balance between the two jets and amounts to f(DP)((D)) = 0.08 +/- 0.01 (stat.) +/- 0.02 (sys.) for jets with transverse momentum p(T) > 20 GeV and rapidity vertical bar y vertical bar < 2.8. This corresponds to a measurement of the effective area parameter for hard double-parton interactions of sigma(eff) = 15 +/- 3 (stat.)(-3)(+5) (sys.) mb.The production of W bosons in association with two jets in proton-proton collisions at a centre-of-mass energy of sqrt(s)=7 TeV has been analysed for the presence of double-parton interactions using data corresponding to an integrated luminosity of 36/pb, collected with the ATLAS detector at the LHC. The fraction of events arising from double-parton interactions, fDP(D) has been measured through the momentum balance between the two jets and amounts to fDP(D) = 0.08 +- 0.01 (stat.) +- 0.02 (sys) for jets with transverse momentum PT>20 GeV and rapidity |y|<2.8. This corresponds to a measurement of the effective area parameter for hard double-parton interactions of sigma_eff = 15 +- 3 (stat.) +5 -3 (sys.) mb.

Search for extra dimensions in diphoton events from proton-proton collisions at (square root)s (equivalent to) 7 TeV in the ATLAS detector at the LHC

The large difference between the Planck scale and the electroweak scale, known as the hierarchy problem, is addressed in certain models through the postulate of extra spatial dimensions. A search for evidence of extra spatial dimensions in the diphoton channel has been performed using the full set of proton-proton collisions at √ s = 7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. This dataset corresponds to an integrated luminosity of 4.9 fb−1. The diphoton invariant mass spectrum is observed to be in good agreement with the Standard Model expectation. In the context of the model proposed by Arkani-Hamed, Dimopoulos and Dvali, 95% confidence level lower limits of between 2.52 TeV and 3.92 TeV are set on the ultraviolet cutoff scale MS depending on the number of extra dimensions and the theoretical formalism used. In the context of the Randall– Sundrum model, a lower limit of 2.06 (1.00) TeV at 95 % confidence level is set on the mass of the lightest graviton for couplings of k/MP l = 0.1 (0.01). Combining with the ATLAS dilepton searches based on the 2011 data, the 95 % confidence level lower limit on the Randall–Sundrum graviton mass is further tightened to 2.23 (1.03) TeV for k/MP l = 0.1 (0.01). Search for Extra Dimensions in diphoton events from proton-proton collisions at √The large difference between the Planck scale and the electroweak scale, known as the hierarchy problem, is addressed in certain models through the postulate of extra spatial dimensions. A search for evidence of extra spatial dimensions in the diphoton channel has been performed using the full set of proton-proton collisions at root s = 7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. This dataset corresponds to an integrated luminosity of 4.9 fb(-1). The diphoton invariant mass spectrum is observed to be in good agreement with the Standard Model expectation. In the context of the model proposed by Arkani-Hamed, Dimopoulos and Dvali, 95% confidence level lower limits of between 2.52 and 3.92 TeV are set on the ultraviolet cutoff scale MS depending on the number of extra dimensions and the theoretical formalism used. In the context of the Randall-Sundrum model, a lower limit of 2.06 (1.00) TeV at 95% confidence level is set on the mass of the lightest graviton for couplings of k/(M) over bar (Pl) = 0.1(0.01). Combining with the ATLAS dilepton searches based on the 2011 data, the 95% confidence level lower limit on the Randall-Sundrum graviton mass is further tightened to 2.23 (1.03) TeV for k/(M) over bar (Pl) = 0.1(0.01).

Search for contact interactions and large extra dimensions in dilepton events from pp collisions at square root of s equals to 7 TeV with the ATLAS detector

A search for nonresonant new phenomena, originating from either contact interactions or large extra spatial dimensions, has been carried out using events with two isolated electrons or muons. These events, produced at the LHC in proton-proton collisions at √ s = 7 TeV, were recorded by the ATLAS detector. The data sample, collected throughout 2011, corresponds to an integrated luminosity of 4.9 and 5.0 fb−1 in the e+e− and μ+μ− channels, respectively. No significant deviations from the Standard Model expectation are observed. Using a Bayesian approach, 95% confidence level lower limits ranging from 9.0 to 13.9 TeV are placed on the energy scale of llqq contact interactions in the left-left isoscalar model. Lower limits ranging from 2.4 to 3.9 TeV are also set on the string scale in large extra dimension models. After combining these limits with results from a similar search in the diphoton channel, slightly more stringent limits are obtained. Search for contact interactions and large extra dimensions in dilepton events from pp

Search for pair production of heavy top-like quarks decaying to a high-pT W boson and a b quark in the lepton plus jets final state at (square root)s (equivalent to) 7TeV with the ATLAS detector

A search is presented for production of a heavy up-type quark (t′) together with its antiparticle, assuming a significant branching ratio for subsequent decay into a W boson and a b quark. The search is based on 4.7 fb−1 of pp collisions at √ s = 7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. Data are analyzed in the lepton+jets final state, characterized by a high-transverse-momentum isolated electron or muon, large missing transverse momentum and at least three jets. The analysis strategy relies on the substantial boost of the W bosons in the t′t̄′ signal when mt′ & 400 GeV. No significant excess of events above the Standard Model expectation is observed and the result of the search is interpreted in the context of fourth-generation and vector-like quark models. Under the assumption of a branching ratio BR(t′ → Wb) = 1, a fourth-generation t′ quark with mass lower than 656 GeV is excluded at 95% confidence level. In addition, in light of the recent discovery of a new boson of mass ∼ 126 GeV at the LHC, upper limits are derived in the two-dimensional plane of BR(t′ → Wb) versus BR(t′ → Ht), where H is the Standard Model Higgs boson, for vector-like quarks of various masses. Search for pair production of heavy top-like quarks decaying to a high-pT W boson and a b quark in the lepton plus jets final state at √ s = 7 TeV with the ATLAS detector

Measurement of Z boson production in Pb-Pb collisions at Square root of s NN equals to 2.76 TeV with the ATLAS detector

The ATLAS experiment has observed 1995 Z boson candidates in data corresponding to 0.15 nb−1 of integrated luminosity obtained in the 2011 LHC Pb+Pb run at √ sNN=2.76 TeV. The Z bosons are reconstructed via di-electron and di-muon decay channels, with a background contamination of less than 3%. Results from the two channels are consistent and are combined. Within the statistical and systematic uncertainties, the per-event Z boson yield is proportional to the number of binary collisions estimated by the Glauber model. The elliptic anisotropy of the azimuthal distribution of the Z boson with respect to the event plane is found to be consistent with zero. ar X iv :1 21 0. 64 86 v1 [ he pex ] 2 4 O ct 2 01 2 Measurement of Z boson Production in Pb+Pb Collisions at √ sNN = 2.76 TeV with the ATLAS Detector

Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using 4.7 fb-1 of (square root) s (equivalent) 7 TeV proton-proton collision data

Weak scale supersymmetry is one of the best motivated and studied Standard Model extensions. It predicts the existence of new heavy coloured particles called squarks and gluinos which are the supersymmetric partners of the quarks and gluons, respectively. The poster summarises results on inclusive searches for supersymmetric squarks and gluinos in events containing jets and missing transverse momentum without leptons. The searches use the full data sample recorded in 2012 at √ s=8 TeV centre-of-mass energy by the ATLAS experiment at the LHC.

Measurement of the cross-section for W boson production in association with b-jets in pp collisions at square root of s equals to 7 TeV with the ATLAS detector

This paper reports a measurement of the W+b-jets production cross-section in proton–proton collisions at a centre-of-mass energy of 7 TeV at the LHC. These results are based on data corresponding to an integrated luminosity of 4.6 fb−1, collected with the ATLAS detector. Cross-sections are presented as a function of jet multiplicity and of the transverse momentum of the leading b-jet for both the muon and electron decay modes of the W boson. The W+b-jets cross-section, corrected for all known detector effects, is quoted in a limited kinematic range, using jets reconstructed with the anti-kt clustering algorithm with transverse momentum above 25 GeV and rapidity within±2.1. Combining the muon and electron channels, the fiducial cross-section for W+b-jets is measured to be 7.1 ± 0.5 (stat) ± 1.4 (syst) pb, consistent with next-to-leading order QCD calculations within 1.5 standard deviations. ar X iv :1 30 2. 29 29 v1 [ he pex ] 1 2 Fe b 20 13 Prepared for submission to JHEP Measurement of the cross-section for W boson production in association with b-jets in pp collisions at √ s = 7 TeV with the ATLAS detectorA bstractThis paper reports a measurement of the W +b-jets (W +b+ X and W +

Measurement of the distributions of event-by-event flow harmonics in lead-lead collisions at square root of sNN equals to 2.76 TeV with the ATLAS detector at the LHC

boverline{b}

Search for a light charged Higgs boson in the decay channel H positive to cs negative in tt negative events using pp collisions at square root of s equals to 7 TeV with the ATLAS detector

+X) production cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC. These results are based on data corresponding to an integrated luminosity of 4.6 fb−1, collected with the ATLAS detector. Cross-sections are presented as a function of jet multiplicity and of the transverse momentum of the leading b-jet for both the muon and electron decay modes of the W boson. The W +b-jets cross-section, corrected for all known detector effects, is quoted in a limited kinematic range. Combining the muon and electron channels, the fiducial cross-section for W +b-jets is measured to be 7.1u2009±u20090.5 (stat)u2009±u20091.4 (syst) pb, consistent with the next-to-leading order QCD prediction, corrected for non-perturbative and double-parton interactions (DPI) contributions, of 4.70u2009±u20090.09 (stat)

Measurement of k T splitting scales in W to lv events at square root of s equals to 7 TeV with the ATLAS detector

_{-0.49}^{+0.60 }